[GRASS5] Re: d.vect.thematic wish: handle null values

[Michael Barton]

Thanks for the clarification Moritz. Is this in the custom breaks section?
This was written by Daniel Calvelo. I'm copying him in case he has any
ideas.

Michael
______________________________
Michael Barton, Professor of Anthropology
School of Human Evolution and Social Change
Arizona State University
Tempe, AZ  85287-2402
USA

voice: 480-965-6262; fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton


> From: Moritz Lennert <mlennert at club.worldonline.be>
> Reply-To: <mlennert at club.worldonline.be>
> Date: Fri, 12 Aug 2005 00:53:33 +0200 (CEST)
> To: Michael Barton <michael.barton at asu.edu>
> Cc: Grass Developers List <grass5 at grass.itc.it>, <dcalvelo at minag.gob.pe>
> Subject: Re: [GRASS5] Re: d.vect.thematic wish: handle null values
> 
> On Fri, August 12, 2005 0:13, Michael Barton said:
>> I'm not sure that nulls are the problem. It won't accept the <= operator.
>> Try straight > and < and see what happens. Also, what is FNR=1?
> 
> The operators are not defined by me but by d.vect.thematic.
> The problem is not the <= operator, but the fact that in the sql statement
> 
> SELECT cat FROM ssbxl01 WHERE revmed >= 7 and revmed<=
> 
> there should be an integer after the <=.
> 
> This integer is missing because the awk script tries to divide by zero because
> of the null values.
> 
> (FNR is an internal awk variable which stands for the "input record number in
> the current input file")
> 
> I can confirm that it is the null values that are the problem since if I
> replace them with any integer value (0, -99999, etc) d.vect.thematic runs
> perfectly, but it creates the classes including the null-replacing integer
> since it doesn't know that they are special values, and there is no way of
> telling it this.
> 
> This is why I plead for one of the two solutions below...
> 
> Hope this helps clarifying the issue.
> 
> All the best,
> 
> Moritz
> 
> 
>> 
>> Michael
>> ______________________________
>> Michael Barton, Professor of Anthropology
>> School of Human Evolution and Social Change
>> Arizona State University
>> Tempe, AZ  85287-2402
>> USA
>> 
>> voice: 480-965-6262; fax: 480-965-7671
>> www: http://www.public.asu.edu/~cmbarton
>> 
>> 
>>> From: Moritz Lennert <mlennert at club.worldonline.be>
>>> Reply-To: <mlennert at club.worldonline.be>
>>> Date: Thu, 11 Aug 2005 23:20:00 +0200 (CEST)
>>> To: Grass Developers List <grass5 at grass.itc.it>
>>> Cc: <michael.barton at asu.edu>, <dcalvelo at minag.gob.pe>
>>> Subject: d.vect.thematic wish: handle null values
>>> 
>>> Hi,
>>> 
>>> Trying to make maps with d.vect.thematic I have stumbled upon the problem
>>> that
>>> the module fails when there are null values in the table (postgresql):
>>> 
>>> **********
>>> awk: (FILENAME=- FNR=1) fatal: division by zero attempted
>>> 
>>> 
>>> Thematic map legend for column revmed of map ssbxl01
>>> 
>>> Value range:   -  33079
>>> Mapped by 7 intervals of
>>> 
>>> Color(R:G:B)    Value
>>> ============    ==========
>>> 0:0:250         7 -
>>> DBMI-Postgres driver error:
>>> Cannot select:
>>> SELECT cat FROM ssbxl01 WHERE revmed >= 7 and revmed<=
>>> ERREUR:  L'opérateur n'existe pas : integer <=
>>> HINT:  Aucun opérateur correspond au nom donné et aux types d'arguments.
>>> Vous
>>> devez ajouter des conversions explicites de type.
>>> 
>>> 
>>> 35:0:215                 -
>>> DBMI-Postgres driver error:
>>> Cannot select:
>>> SELECT cat FROM ssbxl01 WHERE revmed >  and revmed<=
>>> ERREUR:  syntax error sur ou près de «and» at character 41
>>> 
>>> etc...
>>> ************
>>> 
>>> Now I can see two theoretical solutions to this:
>>> 
>>> 1) handle null values
>>> 2) allow to give a value that represents null values (e.g. -99999)
>>> 
>>> For both of these solutions, d.vect.thematic should offer the choice of a
>>> color for these values, so that they do not use the same color scheme as the
>>> 'valid' values.
>>> 
>>> Moritz
>>> 
>> 
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> 
>